A Mechanism for Solute Segregation to Grain Boundaries

1989 ◽  
Vol 159 ◽  
Author(s):  
Chu Youyi ◽  
Zhan Sanhong
Keyword(s):  
Grain Boundaries ◽  
Solute Atom ◽  
Local Equilibrium ◽  
Isothermal Holding ◽  
Boundary Segregation ◽  
Alloy System ◽  
Solute Segregation ◽  
Boron Segregation ◽  
Austenite Grain ◽  
Equilibrium Segregation

ABSTRACTBased an the local equilibrium among vacancies, solute atans and vacancy-solute atom complexes, a mechanism for solute segregation to grain boundaries is suggested for a alloy system with binding energy of complex S≫kT. A set of dynamic equations for grain boundary segregation is ived, which can describe both equilibrium and nonequilibrium segregations, as the effect of the equilibrium segregation is taken into account in the bonndary condition. Theoretical calculation is made by computer for boron segregation at austenite grain boundaries as functions of isothermal holding time, cooling rate and quenching teaperature, which agree well with experimental results.

Non-equilibrium segregation of boron at austenite grain boundaries

1991 ◽  
Vol 10 (20) ◽  
pp. 1232-1234 ◽  
Author(s):  
Shenhua Song ◽  
Zhexi Yuan ◽  
Tingdong Xu
Keyword(s):  
Grain Boundaries ◽  
Austenite Grain ◽  
Equilibrium Segregation ◽  
Non Equilibrium

Role of Grain Boundary Segregation in Austenite Decomposition of Low-Alloyed Steel

2007 ◽  
Vol 558-559 ◽  
pp. 965-970 ◽  
Author(s):  
Shigeru Suzuki ◽  
M. Tanino
Keyword(s):  
Boron Nitride ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Austenite Decomposition ◽  
Microstructure Observation ◽  
Austenite Grain ◽  
Auger Spectra ◽  
Low Alloyed Steel ◽  
Manganese Steels

The influence of addition of small amounts of boron and nitrogen on the microstructure formed by austenite decomposition in low-alloyed manganese steels was investigated. In order to understand microstructural changes by addition of boron and nitrogen, Auger electron spectroscopy was used for analyzing prior austenite grain boundaries in steels doped with phosphorus, boron and nitrogen. The results by microstructure observation showed that the formation of Widmanstätten ferrite was suppressed by addition of a small amount of boron in the steels, whereas Widmanstätten ferrite appears to be formed again by addition of boron and nitrogen. The Auger spectra showed that small particles of boron nitride were detected on grain boundaries in steel doped with boron and nitrogen, while boron was segregated at grain boundaries in steel with boron. This indicates that segregation of boron at grain boundaries and/or sub-boundaries may suppress the formation of Widmanstätten ferrite, while the formation of boron nitride seems to be ineffective to suppression of the formation of Widmanstätten ferrite in steels doped with boron and nitrogen.

Fracture Modes in Ll2 Compounds

1988 ◽  
Vol 133 ◽  
Author(s):  
C. L. Briant ◽  
A. I. Taub
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Intermetallic Compounds ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Fracture Modes ◽  
Beneficial Effects ◽  
Boron Segregation ◽  
Total Composition ◽  
Carbon Additions

ABSTRACTThis paper reports a study of grain boundary segregation and fracture modes in Ll2 intermetallic compounds. Data obtained on Ni3A1, Ni3Si, Ni3Ga, Ni3Ge, and Pt3Ga will be presented. It will be shown that the amount of boron segregation and its ability to improve cohesion depends on the total composition of the compound. The beneficial effects of boron can be counteracted by the presence of borides on the grain boundaries. Carbon additions also produce some improvement in ductility in Ni3Si.

Monte Carlo Simulation of Solute-Atom Segregation at Grain Boundaries In Single-Phase Binary Face-Centered Cubic Alloys

1998 ◽  
Vol 4 (S2) ◽  
pp. 764-765
Author(s):  
David N. Seidman ◽  
John D. Rittner ◽  
Dmitry Udler
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Solute Atom ◽  
Boundary Segregation ◽  
Grain Boundary Segregation ◽  
Diffusional Creep ◽  
Boundary Structure ◽  
Temper Brittleness ◽  
Face Centered Cubic ◽  
Boundary Properties

Solute-atom segregation to grain boundaries has been of interest since the 1930's when it was realized that some steels were susceptible to failure by intergranular fracture when certain impurities were present. Segregation of impurities or intentionally added alloying elements at grain boundaries can greatly affect various grain boundary properties, which in turn affect numerous macroscopic properties. Materials phenomena that have been linked to grain boundary segregation include temper brittleness, fatigue strength, adhesion, precipitation, diffusional creep, intergranular corrosion, and grain boundary diffusivity. Although grain boundary segregation has been extensively studied for many years, the effects of different grain boundary structures on segregation was generally not considered. It has been established both experimentally and theoretically that the level of segregation varies from grain boundary to grain boundary in the same alloy, but there is little direct information on how grain boundary structure influences segregation.

A Comparison of Stem-EDX and Auger Analysis of Segregation: The Plaudits and the Pitfalls.

1997 ◽  
Vol 3 (S2) ◽  
pp. 539-540
Author(s):  
G.J. Tatlock
Keyword(s):  
Grain Boundaries ◽  
Potential Problem ◽  
High Spatial Resolution ◽  
Boundary Segregation ◽  
Line Profiles ◽  
Auger Analysis ◽  
X Ray ◽  
Counting Statistics ◽  
Electron Energy Loss ◽  
Equilibrium Segregation

Equilibrium segregation to grain boundaries has been studied for many years, but only recently have the techniques to quantify such segregation at high spatial resolution become widely available. These include, for example, the Auger surface analysis of fractured samples, or the study of boundaries edge-on in a field emission gun STEM equipped with energy dispersive X-ray analysis or electron energy loss spectroscopy. The key question, however, is whether these different techniques yield the same results when applied to a specific set of samples, and this paper reviews some of the successes and problems associated with such studies.For STEM analysis of grain boundary segregation, several instruments now routinely give probe sizes of ∼1nm. Hence line profiles across grain boundaries at this level of resolution are quite feasible. However a larger probe with greater probe current and better X-ray counting statistics is often more useful, especially if sample drift is a potential problem.

scholarly journals Detection of Solute Segregation at Grain Boundaries

1980 ◽  
Vol 38 ◽  
pp. 360-361
Author(s):  
J. Briceno-Valero ◽  
R. Gronsky
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Segregation ◽  
Solute Concentration ◽  
Boundary Region ◽  
Solute Segregation ◽  
Spectroscopic Techniques ◽  
Concentration Gradients ◽  
X Ray ◽  
Grain Boundary Plane

Studies of grain boundary segregation in metallurgical systems are traditionally based upon the premise that grain boundaries are more likely sites for solute atoms than their surrounding grains. This idea is manifested in experimnental studies which distinguish the solute concentration at boundaries from that of grain interiors using various spectroscopic techniques, including more recently, energy dispersive X-ray analysis in TEM/STEM instruments. A typical study therefore usually consists of spot or line scans across a grain boundary plane in order to detect concentration gradients at the boundary region. It has also been pointed out that there are rather severe problems in quantitatively determining the absolute solute concentration within the grain boundary, and data correction schemes for this situation have been proposed.

Effect of Isothermal Holding Temperature on NGS Kinetics of Phosphorus and Temper Embrittlement

2007 ◽  
Vol 348-349 ◽  
pp. 549-552
Author(s):  
Jun Wang ◽  
Qing Fen Li ◽  
Er Bao Liu
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Isothermal Holding ◽  
Boundary Segregation ◽  
Temper Embrittlement ◽  
Solution Treatment ◽  
Grain Boundary Segregation ◽  
Solution Temperature ◽  
Kinetics Of ◽  
Holding Temperature

When failure occurs in material, it is often occurs by fracture along some grain boundaries and often by the micro-segregation of embrittling impurity to the grain boundaries. In the present work, the non-equilibrium grain-boundary segregation (NGS) kinetics of phosphorus and the temper embrittlement at the same solution treatment and different isothermal holding temperature in steel 2.25Cr1Mo are studied. The NGS kinetics curves of phosphorus at the same solution temperature （1050 oC ）and different isothermal holding temperature (540 oC and 600 oC) are given. Experimental results provide a direct evidence of NGS kinetic model and show that the grain boundary segregation concentrations of phosphorus for specimen isothermal holding at 540 oC are higher than those at 600 oC. The peak values of AES patterns of solute atoms for specimen isothermal holding at 540 oC are also higher than those at 600 oC. It is therefore concluded that the lower the isothermal holding temperature, the higher the segregation concentration of phosphorus at the grain-boundaries, and also the higher the degree of embrittlement.

Two types of boron segregation at austenite grain boundaries and their mutual relation

1990 ◽  
Vol 25 (3) ◽  
pp. 1739-1744 ◽  
Author(s):  
Xu Tingdong ◽  
Song Shenhua ◽  
Yuan Zhexi ◽  
Yu Zongsen
Keyword(s):  
Grain Boundaries ◽  
Mutual Relation ◽  
Boron Segregation ◽  
Austenite Grain

Anisotropic Grain Boundary Segregation in Y-Doped TiO2

2001 ◽  
Vol 7 (S2) ◽  
pp. 280-281
Author(s):  
G. D. Lian ◽  
A. Susalla ◽  
E. C. Dickey
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Level Structure ◽  
Boundary Segregation ◽  
Solute Segregation ◽  
Grain Boundary Segregation ◽  
Boundary Misorientation ◽  
Mole Percent ◽  
Dielectric System ◽  
Grain Boundary Misorientation

A variety of properties of polycrystalline TiO2, such as conductivity, creep and grain boundary diffusion, are strongly dependent on the atomic-level structure and chemistry of grain boundaries. TiO2 has been studied as a model dielectric system because of its relatively simple structure and well-understood point defect chemistry. Defect segregation in grain boundaries of polycrystalline and bi-crystal TiO2 have been studied by several groups and significant variations in solute segregation levels from boundary to boundary were observed. in this paper, we address this issue of anisotropic grain boundary segregation. We have measured solute segregation as a function of grain boundary misorientation to determine any correlation between segregation and misorientation.Yttria-doped TiO2 polycrystalline samples were prepared by mixing 99.999% pure TiO2 powder with 0.1% mole percent 99.99% purity Y(NO3)3 (both powders are commercially available from Aldrich Co. or Alfa Co.), followed by uni-axial pressed to 200-400Pa and sintering at 1300 °C for about 5-7 hours.

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